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    SubjectRe: [patch] x86, perf_counter, bts: add bts to perf_counter
    On Fri, 2009-08-07 at 09:22 +0200, Markus Metzger wrote:
    > Implement a performance counter with:
    > attr.type = PERF_TYPE_HARDWARE
    > attr.sample_period = 1
    > using branch trace store (BTS) on x86 hardware, if available.
    > The from and to address for each branch can be sampled using:
    > PERF_SAMPLE_IP for the from address
    > PERF_SAMPLE_ADDR for the to address

    The patch seems to forget one fundamental aspect, it doesn't provide a

    The 'fake' fixed purpose counter we create only provides event samples,
    but it does not provide a counter abstraction, so people who'd expect
    read() to return the current count of things will get 0.

    We could fix this by keeping a software counter along with it that
    counts the number of BTS entries processed so far.

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      Last update: 2009-08-07 18:43    [W:0.933 / U:7.016 seconds]
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